After countless days of training, napping and training some more, the uber-prepared U.S. women's gymnastics team was given Saturday off - a rare and telling sign that Martha Karolyi believes they are ready.

Led by three-time world champion Simone Biles, the U.S. women are heavily favored to defend the team gold medal they won at the 2012 London Games.

If the expectation or the global spotlight is rattling them, there is no evidence. They are as well-schooled in composure as they are a basic cartwheel.

"We're just so well prepared that we know exactly what to expect of ourselves and our gymnastics once we go out on the competition floor, so nothing here has wowed me," said Biles following Friday's training session, the first time the team practiced in the arena and on the equipment they'll use in competition. "If you think about it (being the Olympics), your brain might fall out! You'd freak out!"

So instead, they'll think of every phase of their Rio Olympics, which gets under way with Sunday's qualifying, as a national championship - something familiar that they've been through many times.

The two eldest on the five-woman squad - team captain Aly Raisman, 22, and Gabby Douglas, 21 - know what it's like to compete and triumph at an Olympics. Both were major contributors to the 2012 team gold in London. In addition, Raisman won gold on floor exercise, and Douglas claimed the sport's biggest individual prize, gold in the all-around.

At 16, New Jersey's Laurie Hernandez is the squad's youngest member. And her gymnastics sparkle with electric energy of youth, as if a dark thought has never crossed her mind.

Biles, the team's competitive anchor, is so far superior to her rivals around the world, both in terms of the difficulty of her skills and the amplitude of their execution, that it's easy to forget she is a first-time Olympian.

She smiled throughout her interviews Friday and giggled that everyone in the Athletes' Village is so tall that she fears, at 4 feet 9, she might get stepped on. But pound for pound, Biles may be the strongest athlete in Rio, and her mental strength is equally formidable.

But the best news for the U.S. women is the surge that Douglas has made since being named to the Rio squad despite a seventh-place finish at the U.S. Olympic trials in July.

Karolyi, the U.S. national team coordinator who played a major role in developing such Olympic champions as Nadia Comaneci and Mary Lou Retton, knows from experience that Douglas has a gift for raising her performance level at the 11th hour.

Just four weeks ago, Douglas's falls from the balance beam on both nights of trials alarmed many, triggering concern that her many marketing obligations and a third coaching change since London had left her ill prepared. But Douglas was rock solid in Friday's practice. She completed her beam routine without a bobble and was a beauty on the uneven bars, where she's a particular asset to the team, her 2 1/2-inch growth spurt since 2012 further elongating the elegant lines of her physique.

"I know Gabby for many years," Karolyi said, obviously pleased by the practice. "She is someone peaking a little bit later. She definitely needs a very organized and structured training system. What we installed before (Olympic) competition, she reacted very well to that. She responded very, very well, so we were able to do good improvements. I feel that she is ready to compete."

Douglas said as much, alluding to the strides she has made since Karolyi sequestered her Olympians for an intensive, highly regimented tune-up camp prior to Rio. "When Martha just instructs, really just pushes us to do our best, it's good for our endurance and our mental game," Douglas said. "She kind of has us in her little bubble. We're in our bubble. It's great. And it whips us into shape."

It showed on Friday, with all five U.S. gymnasts completing their four routines - on floor exercise, vault, uneven bars and beam - without a hitch. That's a 20-for-20 success rate.

That standard stood in stark contrast to the countries that shared the practice window with them; the drop-off in depth from their first to fifth gymnast was evident to even unschooled eyes.

China, Russia and Britain are considered medal contenders as well. But no women's gymnastics teams boasts the depth of the United States.

Aimee Boorman, Biles's longtime coach who is also serving as head coach of the U.S. women's team and will be their primary voice and cheerleader on the competition floor, said she and Karolyi expected nothing less than a clean run-through this week.

"Honestly, the way we train, we would expected them to hit 20 (of 20) because they put in the numbers in the workouts," Boorman said.

The solid practice proved once again that Douglas is among those rare athletes who rises when the stakes are highest. It was also proof also that Karolyi's judgment in assembling Olympic teams is not to be trifled with.